In horses how long does it take to kill worms after a dewormer?

It depends on the dewormer and the type of worm. For example, some dewormers, such as ivermectin, kill worms within a few hours, while others, such as fenbendazole, may take several days to kill all of the worms. Additionally, some worms, such as tapeworms, may require a different type of dewormer than other types of worms. It is important to follow the directions on the dewormer package carefully and consult with your veterinarian if you have any questions about how long it will take for the dewormer to kill worms.